One of the potential uses of organic photovoltaic technology is the manufacture of wearable electronics – for example, devices that can be attached to clothing to monitor medical devices without the need to replace batteries. However, the researchers found that it was difficult to achieve waterproofing without the use of an additional layer, as this would ultimately reduce the flexibility of the membrane. Researchers at RIKEN's Center for Emerging Matter Sciences and their partners have created a flexible, waterproof organic photovoltaic film. This innovative film allows solar cells to be integrated into clothing and remains functional even after rain or washing.
Now, a team of scientists has published research in Nature Communications that does just that. The challenge was to overcome a key limitation of previous equipment, which was the difficulty of making it waterproof without sacrificing flexibility. Photovoltaic thin films are usually made up of several layers. One layer is the active layer, which captures a certain wavelength of energy from sunlight and uses this energy to separate electrons and "electron holes" into cathodes and anodes. The electrons and holes can then be reconnected by the circuit, producing electrical energy. In previous devices, the layers that transport electron holes were usually formed sequentially by layering.
However, in the current work, the researchers deposited the anode layer (in this case, the silver electrode) directly on the active layer, resulting in better adhesion between the layers. They used a thermal annealing process that exposed the film to air at 85 degrees Celsius for 24 hours. "Forming this layer was challenging, but we are excited to complete the task and ultimately produce a film that is only 3 microns thick, and we look forward to seeing the test results," said Xiong, the paper's first author. "
The test results are encouraging. First, they completely immersed the film in water for four hours and found that it still retained 89% of its original properties. They then stretched the film 30% underwater up to 300 times and found that even with such endurance tests, the film still maintained 96% of its performance. In the final test, they put the film in the washing machine for a cycle of washing, and the result was that the film withstood the test in a way that had never been done before.
Kenjiro Fukuda, one of the corresponding authors of the paper, said, "What we have created is a method that can be used more widely. Going forward, by improving the stability of the device in other aspects, such as exposure to air, strong light, and mechanical stress, we plan to further develop our ultra-thin organic solar cells so that they can be used in truly practical wearable devices. "
编译来源：ScitechDaily